Devices to stimulate or regulate cardiac function have been known and used for decades. They involve a power source (pacemaker) and one or more surgical electrodes to attach the source to the heart. They are generally of two types.
Implantable pacers are intended for long-term use and, as the name suggests, are entirely implanted in the body. The other type is intended for temporary use. The temporary pacemaker is located outside the body and is connected to the heart by a surgical electrode called a "temporary pacing wire." Although surgical electrodes are used for preparing electrocardiograms and other applications, for the sake of brevity, the description that follows is focused on temporary pacing wires.
In general, such wires are constructed of a number of fine stainless steel wires braided or twisted together to form a single, flexible, multi-strand electrode wire. The major portion of the wire is electrically insulated with a polyethylene, polytetrafluoroethylene, silicon, nylon, or another non-conducting coating, with a short length of wire at either end left uninsulated. With respect to the conventional temporary pacing wires, to the distal uninsulated end of the electrode wire there is attached, by swaging or other means, a fine curved needle for piercing the heart tissue to place the uninsulated end of the electrode in the myocardium. At the proximal end of the electrode wire, a straight (e.g., Keith-type) cutting needle is attached for piercing the thoracic wall to lead the electrode to an outer point for connection with the pacemaker. Once that has been accomplished, the needle or its sharp-pointed end is clipped or broken and the proximal end of the electrode is readied for attachment to the pacemaker as required to stimulate or regulate the beating of the heart. A single setup involves two electrodes, i.e., two temporary pacing wires.
During the time that the temporary pacing wire is performing its function, the uninsulated end of the electrode must remain anchored in the myocardium. The anchorage of the uninsulated end of the electrode to the myocardium must be secure, lest the continually beating heart cause the wire to be expelled from the myocardium. Conventionally, the electrode is sutured directly to the myocardium, or it is attached to a pad which in turn is sutured to the myocardium. Suturing causes trauma to the heart tissue. Additionally, when the need for the pacing wire has passed, it is necessary to remove from the body the wire that runs from the external pacemaker to the myocardium. The removal of the sutured wire can also cause trauma.